ssh to the server using the mpxadmin account, then su - to root.
run the "net" command and list your settings.
the Primary/audio host name: should be just the server name and NOT the FQDN.
the RTMP host name: should also be just sub-domain.servername and NOT the FQDN
the Domain name: should be only the domain name.
here is an output from my server.
Primary/audio host name: meetingplace
HTTP host name: meetingplace
RTMP host name: web.meetingplace
Domain name: domain.com
so the FQDN for my server is meetingplace.domain.com and web.meetingplace.domain.com
you need to reboot the server if you make changes.